Four things I would check first with NestJS if a bank's API kept leaking sensitive data

Short summary

A practical security guide for NestJS APIs in banking, covering four common data-leak vectors: returning raw entity objects without field exclusion, missing per-record authorization checks, sensitive data in logs, and unshaped responses. Each issue includes concrete code examples and fixes using ClassSerializerInterceptor, ownership guards, and redacting logger interceptors. The article is ordered by the author's real-world triage priority.

• •Return shaped DTOs with @Exclude on sensitive fields instead of raw entities
• •Add ownership guards that verify the user owns the specific record, not just that they're authenticated
• •Redact sensitive fields in logging interceptors to prevent plain-text data leaks in log files

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